S.KEY 684-685J DIAPHRAGMATIC HERNIA 507

the opening through the abdominal wall closed. In some cases the defect
must be repaired \vith fascial sutures used like a lattice \\ork. Strangula-
tion has occurred.

Sciatic hernia
This is so rare that it is of little practical importance.

Perineal hernia

Perinea! hernia occurs through the pelvic floor and is also extremely
rare. Lipomas or fibromas originating in the ischiorecial fossa may
simulate hernia, for occasionally they present in the perineum and can
be pushed back towards the fossa.

Litfre's hernia

Littre's hernia is the term applied to a hernia in which Meckel's
diverticulum is the sole occupant of the sac. It is very rare. When strangu-
lation occurs the symptoms are anomalous, for obstruction is not
necessarily present.

Richer*s hernia

In this form part only of the circumference of the bowel is found in
the sac, hence the synonym "partial enlerocele'. It usually comes under Partial
notice in cases of strangulation. As in the variety previously mentioned en*erocele
the symptoms may be anomalous.

III.—DIAPHRAGMATIC HERNIA
685.] This variety of hernia, though not common, is less rare than is
generally recognized. Jt consists of a protrusion of some abdominal
viscus or viscera, in part or as a whole, and with or without a peritoneal
sac, into the chest cavity. The cases can be conveniently classified as:
(i) traumatic; and (ii) non-traumatic, either congenital or acquired.
Cases of the traumatic type result from severe crushes of the chest or Traumatic
from such injuries as stabs or gun-shot wounds. The defect is generally
in the dome of the diaphragm.
The non-traumatic type can best be understood by reference to Non-
embryological factors. In the early development of the foetus the pleural naumatlc
and peritoneal cavities form one cavity, but during the third month
of intra-uterine life the development of the diaphragm is completed by
the muscularization of the septum transversum. This takes place in
five portions of the septum; the muscular fibres grow through the mem-
branous structures reaching the dorsal margins last of all. Want of
complete development of any one portion, or failure of fusion between
the various portions which go to complete the whole structure, may
result in a defect through which the hernia occurs. The presence of the
great bulk of the liver on the right side explains why the hernia is so